Dust extraction



T. G. NYBORG DUST EXTRACTION May 14, 1940.

Filed NOV. 16, 1937' Fig. 2.

ATTORNEY Patented May 14, 1940 UNITED STATES PATENT OFFICE DUST EXTRACTION Tage Georg Nyborg,

Worcester, England, aa-

Application November 16, 1937, Serial No. 174,865

In Great Britain 4 claims.

This invention relates to the extraction of dust from air and gases and has particular though not exclusive application to the collecting of coal dust at such points as conveyor loading points.

Attempts have been made to extract dust particles suspended in a stream of air or gases by spraying the stream with water or steam jets, the intention being to wet the particles and so increase their effective weight beyond that which can be supported by the gaseous stream. These attempts have hitherto been successful only to a very limited extent, due, it is believed to the difliculty of obtaining eflicient wetting of the dust particles.

The present invention is based on experiments which have shown that intimate mixing of dust and water particles can be obtained by directing a fine, gradually divergent water spray along the axis of a mixing tube through which the dust laden air stream is passed with a rotary movement of the air about the tube axis. When the characteristics of the air stream and the shape and position of the spray nozzle are suitably selected for efficient extraction of the dust from the air, the dust-and-water particles form a rather ilrm sludge which is ldeposited on the sides of the tube and builds up into a vena contracta form.

It is an object of the invention to provide methods for the extraction of dust from air and gases based upon these experimental results.

Further, in addition to obtaining the rotary motion of the air column about the axis of the tube, conditions are preferred which will tend to give the dust laden air a subsidiary rotation about ring axes which lie in planes perpendicular to the axis of the tubes. The subsidiary vortex movement of the air serves to bring the dust particles into intimate contact with the water spray and to improve the wetting of the particles.

The rotary motion of the air column in the mixing tube can be produced in any suitable manner. stream is led tangentlally into an annular chamber into which the end oi the mixing tube projects axially so that the air is given a rotary motion in the annular chamber which is translated into a vortex motion in the mixing tube. The mixing tube is preferably eccentrically arranged with regard to the annular chamber so that the cross-section of the air stream is gradually reduced as it passes round the chamber.

Other objects of the invention will be clear In one form of apparatus, the air November 21. 1936 from the description which follows and from the claiming clauses.

A specic form of dust extractor, the new or improved features, combinations and arrangements oi parts of which form in themselves parts of the invention, will now be described in some detail with reference to the accompanying drawing in which:

Fig. 1 is a side view of a dust extractor, and

Fig. 2 is a plan view.

In this form, a mixing tube I comprising an open-ended metal cylinder is arranged with its axis vertical. The upper end of this tube I projects into the base of a cylinder 2 of larger diameter than the tube I, this cylinder`2 being closed at the top by a plate 3 and having a tangential inlet 4 in its side wall. Y

Between the side wall of the cylinder 2 and the upper end of the tube I is thus formed an annular chamber 5. The axis of the tube I and oi the cylinder 2 are parallel but are somewhat displaced so that the annular chamber 5 -is of gradually narrowing section, the narrowest part being near the tangential inlet. A partition 6 is arranged across this narrowest part between the cylinder 2 and the tube I so as to direct air entering through the tangential inlet l in'one direction around the annular chamber 5 so that the cross-section of the air stream round the annular chamber gradually decreases.

A spray nozzle 1 is mounted in the top plate 3 coaxially with the tube I and is arranged to direct a flne gradually divergent spray of water along the axis of the tube I. 'I'he spray is of such an angle that the water does not come into contact with the side of the tube I for at least a considerable length of the tube.

The lower end of the mixing tube I projects into a depositing chamber 8. This chamber is, in the form shown, formed by the lower part of a casing 9 divided into two parts by a partition plate I0. The mixing tube I passes through the upper part of the casing 9 and through the cnr tition plate and opens into the chamber 8.

A vertical tube II, parallel to the mixing tube I, also opens into the depositing chamber 8 and passes through the upper part of the casing 9. This tube II is closed at the top by a plate I2 and has an outlet I3 in the side thereof. This outlet I3 is connected by a short horizontal tube I1 to the inlet Il of an extractor fan I5 driven by an electric or other motor I6 mounted on the top of the casing 9. The fan I5 exhausts through its outlet I8 into the upper part Il oi' the casing I i'rom'wh'ich there is an outlet 2l to the mosphere' at one end oi the casing- The depositing chamber I is closed at each end by doors 2| which are readily removable but substantially air-tight. Each door has projecting hooks 22 which ilt over the edge oi.' a rim 23 at the bottom of the opening into the chamber and brackets 24 at each side.. These brackets are formed with tapered slots 26 in their lower edges which engage with pins 26 at the topo! the chambert. The doors. can bereadily removed by lifting them vertically by means o! the handles 21 and as readily replaced. the sides of the tapered slots 25 engaging the pins 2l and drawing the doors in a substantially airtight manner against the casing 9.

The dust-laden air is drawn into the extractor by means of the i'an I6. It enters through the tangential inlet 4, passes round the annular chamber l being thus given a rotary movement and then passes down the mixing tube I. In passing from the annular chamber ,I to the tube I, the air appears to be given a subsidiary rotary movement about ring axes concentric with the axis of the tube. The air passing down the tube I retains its rotary motion and in effect creates a vortex system in the tube, this vortex system comprising a main vortex rotating about the axis of the tube and subsidiary vortices rotating about ring axes in planes perpendicular to the axis of the tube. l

The ilne spray of water from the spray nozzle I occupies the centre of the main vortex system and dust particles in the air come into intimate contact with xthe water particles and are thoroughly wetted. The 4wetted particles adhere to the wall of the tube I and form arather firm sludge which builds up on the tube wall in the Y form of a vena con-tracts. somewhat of the general shape shown in dotted lines in Fig. 1.

The sludge builds up on the wall towards the centre of the tube until the vena contracta is formed (actually with a rough surface after the fashion of small breaking waves coming into a beach) and thereafter pieces of the sludge (representing the crests of the waves) break ofi from the deposit (and fresh waves build up) so that the tube becomes self-cleaning. The sludge breaking oif falls into the depositing chamber 8 from which it canvbe removed through the doors 2|. f l

'Ihe air passes into the depositing chamber 8 which is of greater cross-sectional area than fthe tube I so that wetted dust still canied by the air stream drops out into the depositing chamber because of the decrease in the air velocity. From the depositing chamber, the air stream passes up the tube II and through the extractor fan I5 into the part Il ct the casing I andthence'to the outside of thc'apparatus through the outlet 20.

I claim:

1. Apparatus i'or extracting and collecting dust from air or gases comprising a chamberf amixing tube open at its end projecting into the chamber and forming therewith an annular space. means for leading drust laden air tangentiaily into this annular space so asto impart a rotary motion to the air, and causing the rotating air to pass inwardly into the mixing tube over the projecting end thereof so that a vortex is formed tending to throw dust particles towards the center thereof, and a spray nozzle arranged near the entrance to the mixing tube to deliver a fine water sprayv along the axis of the vortex thus formed in the direction of its general movement.

2. Apparatus for extracting and collecting dust from air or gases comprising a chamber, a mixing tube open at its end projecting into the chamber and `forming therewith an annular space, means for leading dust laden air tangentially into this annular space so as to impart a rotary motion to the air, and causing the rotating air to pass inwardly into the mixing tube over the projecting end thereof so that a vortex is formed tending to throw dust particles towards the center thereof, a spray nozzle arranged near theentrance to the mixing tube to deliver a iine water spray along the axis of the vortex thus formed in the direction of its general movement and a depositing chamber to receive and retain dust-and-water particles from the mixing tube and arranged to be traversed by the air before it emerges.

3. Apparatus for thel extraction and lcollection of dust from dust-laden air or gases comprising an annular chamber having a tangential inlet and a substantially axial outlet, a mixing tube coaxial with this outlet and.y projecting into the annular chamber so that the air passing through the mixing tube is caused to rotate asa whole about the axis cf the tube and to enter it with an inward rotational movement, a spray'nczzle arranged to direct a line spray along the'axis of the mixing tube, in the general direction of travel of the air and a chamber arranged to receive sludge coming away from the wall ofthe mixing tube.

4. Apparatus for extracting and collecting dust from air or gases as deiined in claim 3 in which the mixing tube i-s arranged so that the general direction of flow of -air through the tube is down-v wards.

TAGE GEORG NYBORG. 

